Barrel plating



July 22, 1958 A. R. HOFFMAN 2,

BARREL PLATING Filed June 21. 1954 4 Sheets-Sheet 1 .T. TIME swrrcu JNVEN TOR. A0605? 2. HOFFMAN ATTOENEYfi Jilly 22, 1958 A. R. HOFFMAN 2,844,528

. BARREL 'PLATING I Filed June 21.. 1954 4 Sheets-Sheet 2 ATTORNEY INVENTOR.

) A0605; 2. Hor'gMAN f 'fizg July 22, 1958' A. R. HOFFMAN 2,344,523

- BARREL PLATING V I Filed June 21, 1954 4 Sheets-Sheet 3 INVENTOR. AUGUST ,8 HOFFM N July 22, 1958 r A. R. HOFFMAN 2,844,523

- BARREL PLATING,

Filed June 21. 1954 4 Sheets-Sheet 4 5'6 I I I IN V EN TOR. AUGUST E2 HOFFMAN BEL PLATRNG August R. Hellman, Cleveland, Uhio Application lune 21, 1954, Serial No. 438,281

\\ 4 Claims. (Cl. 204-23) My invention relates to electroplating and concerns particularly improved arrangements for barrel plating.

It is an object of my invention to accomplish safe, eflicient, economical plating of articles in electroplating baths.

A specific object is to avoid excessively heavy deposits and unduly prolonged passage of electroplating current.

Another object is to avoid arcing, hydrogen explosions, splashing of electrolyte and hazard to personnel.

'Still another object is to provide automatic initiation and cutoff of plating current flow in barrel plating systems to prevent flow of current except when the barrel is in place with articles to be plated fully immersed in the electrolyte.

A further object is to interrupt large currents in low voltage circuits efficiently and economically and to pro vide inexpensive, readily installed, durable apparatus therefor.

Other and further objects, features, and advantages of the invention will become apparent as the description proceeds.

In carrying out the invention in accordance with a preferred form thereof in barrel plating, I provide a control device interposed in one of the connections from low-voltage bus bars to the tank containing the rotatable barrel. The control device comprises a pair of plates composed of high-conductivity metal mounted in spaced relation to each other and a plurality of unitary contactor units supported between said plates by bolts serving as electrical terminals thereof. Each contactor unit has windings and all windings are connected in parallel as a group, connected in series with contacts of a time switch arranged to close its contacts after the barrel has been lowered into the tank to prevent arcing and splashing of electrolyte with attendant hazard to the operator.

A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanying drawings in which:

Fig. 1 is circuit diagram of an electroplating system forming an embodiment of my invention with a barrel type of electroplating tank represented schematically.

Fig. 2 is a side elevation of a control unit for the system of Fig. 1.

Fig. 3 is a front elevation of the unit shown in Fig. 2.

Fig. 4 is a perspective view of a gear-driven rotating barrel unit partially withdrawn from the plating tank of Fig. 1.

Fig. 5 is a perspective view, corresponding to Fig. 4, drawn to a smaller scale, showing the rotating barrel fully immersed and showing the control unit of Figs. 2 and 3, interposed in bus bar connections to a source of low-voltage, high-amperage plating current.

Fig. 6 is a circuit diagram partially representing schematically an electroplating system forming a modified embodhnent of my invention, and

Fig. 7 is a fragmentary view of a modification of the arrangement of Fig. 6.

Like reference characters are utilized throughout the drawing to designate like parts.

In the barrel plating of relatively small metal articles, to coat them with cadmium, chromium or other plating metal, the articles are supported in an insulating drum provided with internal cathode connections which make electrical contact with the articles. The drum is immersed in a suitable electrolyte in a plating tank and is rotated to insure coating all surfaces of the articles and making the thickness of the coating substantially uniform.

A suitable tank 11 and drum 12 are illustrated in Figs. 4 and 5. An electrolyte 13 of suitable composition, according to the metal to be deposited, is contained in the tank 11. The drum 12 is shown as being of the gear driven type having a ring gear 14 meshing with pinions 15 and 16 driven directly or indirectly by a motor (not shown) for rotating the barrel 12. There is a cradle 17 rotatably supporting the drum 12 with a lifting ring 13 for receiving a crane hook 12 to enable the drum to be removed for unloading and to be immersed in the tank 11 for plating. The drum 12 is provided with openings or made in ribbed form to give free access of electrolyte to the articles in the drum. internal cathode connections 2% are provided consisting of insulated conductor means lying loose within the drum 12 and bare only at the lower end 243A adapted to make contact at the bottom of the drum 12 with metal articles to be plated resting therein in the drum. A suitable removable cover 21 is provided for the drum 12.

For supplying plating current at low voltage of the order of 12 volts, a positive bus bar 22 and a negative bus bar 23 are provided. A control unit 24 is interposed in one of the bus connections. Although the invention is not limited thereto, in the specific arrangement illustrated, the positive bus bar 22 and the anodes (not shown in Fig. 5) are connected to the tank 11 and the control unit 24 is interposed in the connections between the negative bus bar 23 and the drum 211.

A suitable insulating mounting, including insulator blocks 25, is provided to insulate the metallic tank 11 from the drum cradle 17. The bus bar 22 is connected to the tank 11 by a metallic strip 26. As shown schematically in Fig. 1, anodes 27 are also connected to the strip 26 and the bus bar 22.

For making electrical connections to the internal cathode connections 20 in the perforated drum 12, one or more stationary contacts 28 are provided, insulated from the tank 11 but adapted to be connected to the negative bus bar 23 through the control unit 24 as represented schematically in Fig. 1.

As shown in Fig. 2, the control unit 24 comprises a pair of narrow plates or thick strips 29 and 30 of highly conducting metal such as aluminum or copper, bolted to a plurality of contactor units 32 by contact-terminal bolts 33 and 34 serving both as power-current terminals and supports for the contactor units 32. The control unit 24 may also include suitable means for adapting to different plating voltages such as a voltage dropping rheostat 35; and indicator lamps of different colors, e. g. a green lamp 36 and a red lamp 37, are provided. The rheostat 35 is provided with a movable tap 38 mechanically connected to a knob 39 having a pointer 41 cooperating with a dial face 42 graduated in voltage.

The contactor units 32 are of conventional type similar to automobile starting switches but with continuous duty windings preferably, fully encased, each having internal contacts (not visible in Fig. 2) including stationary contacts 43 and 44 connected to the terminal bolts 33 and 34, a movable contact 45 cooperating with the stationary contacts, a plunger or armature 46 mechanically connected to the movable contact and a solenoid winding 47 3 in magnetic relation to the plunger for closing the contacts when the winding is energized. Each solenoid winding as shown in Fig. 2 has a negative terminal 48 and a positive terminal 49. For electrically connecting each of the negative terminals 48 to the negative or rear plate 2.9, a metallic clip 51, preferably of copper is provided.

All of the positive solenoid winding terminals 49 are connected together by a conductor 52, and also connected to the rheostat 35 by a conductor 53 and to one end of the filament of the green lamp 36 by a conductor 54. The filaments of the red and green lamps 36 and 37 have a common terminal 55 connected to the rear or negative plate 29 by a conductor 56. The filament of the red lamp 337 is connected at the other end to the front or positive plate 30 by a conductor 57.

For interrupting the flow of plating current after the current has flowed for a predetermined time sufiicient to produce the desired thickness of metallic coating, a time switch 59 is provided.

The time switch 59 is preferably of a known type, not constituting a part of my present invention, such as the model FAB Timer manufactured by the Industrial Timer Corporation of Newark, New Jersey, for example, which closes contacts 61 a predetermined relatively short time after being energized and reopens the contacts 61 a predetermined adjustable time thereafter. The time switch 59 is represented schematically as being ofa type adapted to be energized by a l-volt alternating-current 62 through a pair of conductors 63. In order to prevent flow of plating current until the drum 12 and cradle 17 have been lowered in position, with the drum 12 immersed in the tank 11, a safety switch 64 is provided having a pair of normally open contacts 65 and 66 interposed in the conductors 63 energizing the time switch 59.

The safety switch 64 is carried by the cradle 17, having the contact 65 secured thereto by an insulator block 67 as shown schematically in Fig. 1. The contact 66 is mounted relatively movable with respect to the contact 65, so arranged that it drops away from the contact 65 by gravity but rests upon one of the insulator blocks 25 so as to be lifted relatively against the contact 65 when the drum 12 is lowered into the tank 11 and the cradle 17 rests thereon.

The method of electroplating described and the apparatus illustrated promote safety and. economy of operation. Arcing, hydrogen explosions and splashing of electrolyte attendant are prevented because the electrical circuit is kept open until the barrel 12 is fully immersed in the electrolyte 13 and is reopened before the barrel 12 need be lifted.

The articles to be plated are loaded into the barrel 12 with the cover 21 removed while the cradle 17 is supported outside the tank 11 by the crane hook 19. Then, after the cover 21 has been replaced, the cradle 17 is lowered in place with the rotating drum 12 immersed in the electrolyte 13 in the position shown in Fig. 5. The action of lowering the cradle 17 causes the safety switch 64 to be closed by bringing the contacts 65 and 66 together and starting operation of the time switch 59. The time switch 59 has been preset for a time duration intended to give the desired thickness of plating. After energization of the time switch 59, the solenoid windings 47 are energized, causing the contactors 32 to close, closing the plating circuit only after the barrel 12 has been immersed in the electrolyte 13.

When the time switch 59 has operated for the predetermined period, its contacts 61 are opened, de-energizing the solenoid windings 47 and causing the plating circuit to be interrupted. So long as the solenoid windings 47 are energized the green lamp 36 connected in multiple therewith is bright, showing that plating is going on. However, as soon as the solenoids 47 have been de-energized and thecontactors opened, the red lamp 37 is energized, informing the operator that the desired thickness of plating has been produced so that the cradle 17 may again be safely lifted preparatory to recharging the drum 12. The automatic interruption of the plating current eifects a saving of the anode metal by avoiding the deposit of excessive metal. It is advantageous also in producing uniformity of the plated articles in successive plating batches. Since the current is interrupted as the cradle 17 is lifted, there is no arcing at the surface of the electrolyte 13 as the cradle is lifted, and no hydrogen explosions can result. Consequently splashing of the electrolyte is avoided, and there is no hazard to the operators from splashing of electrolyte. Moreover, the arrangement avoids arcing at the saddle contacts 28 when the saddle is either lowered or lifted. Consequently burning of these contacts is prevented.

The arrangement illustrated is adapted for breaking circuits carrying 600 amperes or more, and it may readily be adapted for breaking any desired magnitude of current by employing a suitable number of the contactor units 32.

The arrangement isespecially advantageous when plating relatively expensive metals. For example, in plating of cadmium 650 ampere-minutes of electricity represents a consumption of .72 ounce. At a price of $1.75 per ounce of cadmium, there is a loss of $1.75 for each approximately twenty minutes that the barrel is left in the solution by the operator with the current flowing, unless the automatic current interrupting arrangement of my invention is employed to prevent excessive plating. Even though the barrel should be left in the solution after the current is turned off no harm is done as the work is actually benefited by being cleaned and actually having the surface polished or burnished thereby. Nevertheless, in plating certain types of metal such as zinc, for example, it is desirable to cause a relatively small current or trickle current to continue flowing through the electrolyte after the plating current has been out 01f in order to avoid a pickling effect. Accordingly, my invention contemplates the provision of a simple means carrying small current of the order of an ampere or so for continuing the flow of current after the switch contacts 45 are opening. Arrangements for accomplishing this are illustrated in Fig. 6.

Although my invention contemplates the use of a selfcycling timer 59, the invention is not limited thereto and if desired a mechanical time switch 71 may be employed instead of an electric time switch in orderto avoid any need for 1l0-volt connections. Fig. 6 illustrates also an arrangement for adapting the connections of the control windings for either 4 /2 to 6-volt plating circuits or 9 to l6-volt plating circuits without the necessity of dissipating energy in the voltage dropping resistor 35.

Referring to Fig. 6 in accordance with an alternative embodiment of my invention, the contactor units 32 are mounted between aluminum conductor strips 29 and 30, but the solenoid windings 47 are connected in two groups which may be connected either in parallel or in series parallel. As illustrated, one group of solenoid windings 47A, 47B, and 470 is connected in parallel. Each of the negative terminals 48 is connected together and to the aluminum conductor strip 29, and each of the positive terminals 49 is connected together.

The second group of solenoid windings 47D, 47B and 47F is connected in parallel with common positive terminals 72 and common negative terminals 73. A double throw switch 74 is provided for alternatively connecting the groups of solenoid windings in series or series parallel. Although to simplify the drawing a double pole double throw knife switch is illustrated, the switch 74 is preferably of the snap or toggle switch type which remains in one position or another with no open or neutral position.

The switch 74 includes a parallel-position stationary contact 75, connected to the solenoid terminal 72, a parallel-position stationary contact 76 connected to the negative solenoid terminal 48 and to the aluminum conductor strip 29, and a series-position stationary contact 77 connected to the common solenoid terminals 73. The double throw switch 74 also has a movable contact 78 connected to the solenoid terminal 49 and a movable contact 79 connected to the stationary contact 77.

The mechanical time switch or timing clock 71 'has nor mally-open contacts 81 connected between solenoid terminal 72 and positive line 22 of the plating-current source, represented for the sake of illustration as a 12-volt source. The time switch 71 is a conventional timer such as those in which the turning of a knob closes the contacts 81 through cam action and the contacts reopen after the predetermined length of time for which the timer is set.

If desired, for cooling the contactor units 32 a blower 82 may be mounted between the conductor strips of the units of 32. For driving the blower 82, a direct-current motor 83 is provided, wound for approximately 12 volts and drawing a current of approximately one ampere. The blower motor 83 may be employed also as a means for supplying trickle current to the tank after the plating current contacts 45 have opened. To this end the winding of the motor 83 is so connected as to be in a series circuit with the solenoid windings and tank when the contacts 45 are open, but in parallel with the solenoid windings when the contacts 45 are closed. As illustrated, the blower motor 83 is provided with a lead 84 connected to the aluminum plate 30 and a lead 85 connected to the solenoid winding terminal 72.

The windings 47A to 47F are designed for operating efficiently and safely at from 4 /2 to 8 volts. Accordingly when the voltage of the plating source is within this range, the movable contacts 78 and 79 of the double-throw switch 74 are moved to the left. A circuit through the solenoids 47D, 47B and 47F in parallel is then provided from the positive line 22, through the mechanical time switch 71, to the terminal 72, through the windings to the terminal 73, the contact 77 of the switch 74, the movable contact 79 and stationary contact 76, the conductor strip 29 back to the negative lead 23 of the plating source. Likewise there is a circuit from the positive lead 22 of the plating current source, through switch 71 to terminal 72, the stationary contact 75 of the double throw switch 74, the movable contact 78, the conductor 86 to the positive terminal 49 of the solenoid windings 47A, 47B and 47C through the windings in parallel to the negative terminal 48, the conductor strip 29 and back to the negative lead 23 of the plating current source.

On the other hand, for plating at higher voltages of the order of 9 to 16, for example, where the series connection isemployed and the movable contacts 78 and 79 of the double throw switch 74 are moved to the right, a seriesparallel circuit takes place from the positive lead 22 through the time switch 71, the solenoid terminal 72 through the solenoids 47D, 47B and 47F in parallel, to the solenoid terminal 73, the stationary contact 77 of the double throw switch 74, movable contact 78, the conductor 86, the positive terminal 49 of the windings 47A, 47B, and 47C, these windings in parallel to negative terminal 48 thereof, the conductor strip 29 and back to the negative lead 23.

When the contacts 45 are closed and the switch 71 is also closed, the apparatus has been set for causing plating current to flow; the blower motor 83 is energized by a circuit from the positive lead 22 of the plating current source, through the switch 71, the terminal point 72, the conductor 85, the blower motor 83, the conductor 84, the con ductor strip 30, the contacts 45, the conductor strip 29 and to the negative lead 23. On the other hand, after the time switch 71 and the contacts 45 have opened in order to interrupt the plating current and eifect a saving of plating metal, also avoiding hazards in the event the cradle should be lifted, the blower motor 83 is provided with a circuit from the positive lead 22 of the plating current source through the tank 11, the solution therein, the cathode contact means 20A, the cathode connection 20, the stationary contact 28, the strip 30, the conductor 84,

the blower motor 83, the conductor 85, the connection point 72, the solenoid windings 47 either in series or series parallel according to the position of the switch 74, the conductor strip 29 and the negative lead 23. Since the double throw switch 74 is of the snap type, the switch 74 always provides a circuit for the trickle current of the order of an ampere determined by the resistance of the blower motor 83. The trickle current flows continuously through the solution in the tank 11 and the articles contained in the drum 12, thus avoiding pickling action.

In the arrangement of Fig. 6 a mechanical time switch has been disclosed to illustrate an embodiment in which no 1l0-volt connections are required and only a single low-voltage connection need be made in assembling the apparatus. It should be understood, however, that my invention is not limited thereto and that the novel features of Fig. 6 may be employed also in connection with automatic re-cycling timers and time switches energized from l10-volt circuits or other central station lines. For example, as illustrated in the fragmentary view of Fig. 7, the safety switch 64 of Fig. 1 may be mounted in the manner shown in Fig. 1, but connected in series with the plating circuit leads 22 and 23 and the solenoid winding 87 of a relay' 88, having normally open contacts 89 controlling the energization of a re-cyclingtype of automatic time switch 59 as employed in Fig. 1.

Certain embodiments of the invention and certain methods of operation have been shown and particularly described for the purpose of explaining the principle of operation of the invention and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and it is intended therefore, to cover all such modifications and variations as fall within the scope of the invention.

What I claim and desire to secure by Letters Patent of the United States is:

1. An electroplating system for a movable article comprising a metallic plating tank for containing electrolyte, a rotatable barrel composed of electrically insulating material adapted to receive an article to be plated and to be lowered into the tank and supported therein, internal cathode contacts means in said barrel for contacting such articles, anode bars immersed in the tank composed of the metal to be plated on the article adapted to be received in the barrel, first and second bus bars for supplying electric current to the tank, electrical connections between the first of said bus bars, said tank and said anodes, electrical connections between the second of said bus bars and the internal cathode contact means, a control device interposed in one of said connections and comprising first and second plates of highly conducting metal separated from each other by a plurality of unitary, contact-making units mounted between said plates in electric conducting relation, each of said units having therein electrical contacts one of which is connected to one of said plates and the other is connected to the other of said plates, a plurality of solenoid windings, each in operating relation to one of said contacts for closing said contacts when the solenoid is energized, each of said solenoid windings being connected at one end to the second of said bus bars, and at the other end being connected to a common terminal, a time switch having a pair of contacts, said time switch contacts being connected between said solenoid common terminal and said first bus bar, a green signal lamp connected across said solenoid windings in shunt therewith,

a red signal lamp connected between said conducting,

plates, and means in said time switch for closing the time switch contacts after the barrel is immersed in the electrolyte, whereby the current flow commences only after the article-containing barrel has been immersed in the electrolyte and terminates after a predetermined time selected as sufiicient for the desired thickness of coating upon the article in the barrel.

2. In an electroplating system for a movable article, the combination of a plating tank, electric contact means for an article to be plated within the tank, terminals for applying electric plating current, a normally-open circuit making and breaking control device in series with said terminals and said article contacting means, solenoid winding means for making and breaking said electrical contact having an electric circuit, means for interrupting the solenoid winding circuit after a predetermined time duration so that the article to be plated may be lifted without arcing, explosions, and splashing of electrolyte or attendant hazards, and means for automatically continuing a trickle of current through the electrolyte and the article to be plated as soon as the plating circuit is interrupted.

3. Apparatus as in claim 2, wherein the trickle current supply means comprises a motor of a blower mounted to ventilate the circuit making and breaking control device and the motor has a Winding connected between a point common to the solenoid Winding means and the means for interrupting the solenoid winding circuit and a point common to the article contacting'means and the circuit making and breaking control device, whereby the blower motor is energized in parallel with the solenoid winding means when the circuit making and breaking control device is closed, and forms a circuit serially with the solenoid Winding means and the plating tank across the plating current terminals when the circuit making and breaking control device is opened.

4. The method of plating an article by'means of a o revolving barrel adapted to be immersed in an electrolyte and connected in a heavy-current plating circuit which comprises the steps of lowering the barrel with the plating circuit open, closing the circuit, maintaining it closed for a predetermined time until the plating-operationis completc, causing the plating circuit to open automatically,

causing a trickle current to pass through the electrolyte and the plated article as soon as the plating circuit has been interrupted and thereafter lifting the barrel, thereby avoiding heavy arcing, hydrogen explosions, and hazard to the operator from splashing electrolyte.

References Cited in the file of this patent UNITED STATES PATENTS 1,624,728 Graf Apr. 12, 1927 1,787,931 Besold Ian. 6, 1931 1,906,817 Seely May 2, 1933 2,347,777 Hanscom May 2, 1944 2,352,550 Joseph June 27, 1944 2,370,621 Freitag et al Mar. 6, 1945 2,397,522 Baier Apr. 2, 1946 2,469,470 Mageoch May 10, 1949 2,494,121 Grainger Jan. 10, 1950 2,498,128 Lang Feb. 21, 1950 2,532,907 Hangosky Dec. 5, 1950 

1. AN ELECTROPLATING SYSTEM FOR A MOVABLE ARTICLE COMPRISING A METALLIC PLATING TANK FOR CONTAINING ELECTROLYTE, A ROTATABLE BARREL COMPOSED OF ELECTRICALLY INSULATING MATERIAL ADAPTED TO RECEIVE AN ARTICLE TO BE PLATED AND TO BE LOWERED INTO THE TANK AND SUPPORTED THEREIN, INTERNAL CATHODE CONTACTS MEANS IN SAID BARREL FOR CONTACTING SUCH ARTICLES, ANODE BARS IMMERSED IN THE TANK COMPOSED OF THE METAL TO BE PLATED ON THE ARTICLE ADAPTED TO BE RECEIVED IN THE BARREL, FIRST AND SECOND BUS BARS FOR SUPPLYING ELECTRIC CURRENT TO THE TANK, ELECTRICAL CONNECTIONS BETWEEN THE FIRST OF SAID BUS BARS, SAID TANK AND SAID ANODES, ELECTRICAL CONNECTIONS BETWEEN THE SECOND OF SAID BUS BARS AND THE INTERNAL CATHODE CONTACT MEANS, A CONTROL DEVICE INTERPOSED IN ONE OF SAID CONNECTIONS AND COMPRISING FIRST AND SECOND PLATES OF HIGHLY CONDUCTING METAL SEPARATED FROM EACH OTHER BY A PLURALITY OF UNITARY, CONTACT-MAKING UNITS MOUNTED BETWEEN SAID PLATES IN ELECTRIC CONDUCTING RELATION, EACH OF SAID UNITS HAVING THEREIN ELECTRICAL CONTACTS ONE OF WHICH IS CONNECTED TO ONE OF SAID PLATES AND THE OTHER IS CONNECTED TO THE OTHER OF SAID PLATES, A PLURALITY OF SOLENOID WINDINGS, EACH IN OPERATING RELATION TO ONE OF SAID CONTACTS FOR CLOSING SAID CONTACTS WHEN THE SOLENOID IS ENERGIZED, EACH OF SAID SOLENODI WINDINGS BEING CONNECTED AT ONE END TO THE SECOND OF SAID BUS BARS, AND AT THE OTHER END BEING CONNECTED TO A COMMON TERMINAL, A TIME SWITCH HAVING A PAIR OF CONTACTS, SAID TIME SWITCH CONTACTS BEING CONNECTED BETWEEN SAID SOLENOID COMMON TERMINAL AND SAID FIRST BUS BAR, A GREEN SIGNAL LAMP CONNECTED ACROSS SAID SOLENOID WINDINGS IN SHUNT THEREWITH, A RED SIGNAL LAMP CONNECTED BETWEEN SAID CONDUCTING PLATES, AND MEANS IN SAID TIME SWITCH FOR CLOSING THE TIME SWITCH CONTACTS AFTER THE BARREL IS IMMERSED IN THE ELECTROLYTE, WHEREBY THE CURRENT FLOW COMMENCE ONLY AFTER THE ARTICLE-CONTAINING BARREL HAS BEEN IMMERSED IN THE ELECTROLYTE AND TERMINATES AFTER A PREDETERMINED TIME SELECTED AS SUFFICIENT FOR THE DESIRED THICKNESS OF COATING UPON THE ARTICLE IN THE BARREL. 